To turn this screen into a Dark Room, Press D and the top left corner of the screen should show a shady corner to indicate that the room is dark.

Alternatively, you can take the long route of toggling this by going to Screen→Screen Data. Under the S.Flags 1 tab, check Dark Room.

To preview the room and see how it looks with the lights out, Press L. There is no menu option for toggling this, so this is a keyboard button to remember if you use Dark Rooms often.

While the room is definitely darker, it's still rather easy to navigate it without using the candle. To fix this, we need to draw the floor using CSet 3. A quick way to fix this is to use Color Set Fix.

Select CSet 3 then go to Tools→Color Set Fix. Make sure Dungeon Floor is selected and press OK.

The blocks in the room should now have a red tint. If you hover the mouse cursor over various combos on the floor, they should show up as CSet 3. The preview for the dark room should also now look better.

Now there is actually a disadvantage to the player leaving the room dark since you can't see everything in it.

The blocks on the screen we've been working with for this page are of the combo type Push (Wait). This means that you cannot push them until all enemies in the room are dead. A method to speed this up for the player would be to allow them to kill all of the enemies in the room quickly.

Enemy Ringleaders are one way of speeding things up. If you kill the enemy that is designated as the ring leader, all remaining enemies in the room will instantly die. Let's try that out for Map 3→Screen 50.

Go to Screen→Screen Data (F9) and go to the E.Flags tab. Select First Enemy Is 'Ring Leader'.